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-rw-r--r--src/pdkim/signing.c903
1 files changed, 903 insertions, 0 deletions
diff --git a/src/pdkim/signing.c b/src/pdkim/signing.c
new file mode 100644
index 0000000..d78f31a
--- /dev/null
+++ b/src/pdkim/signing.c
@@ -0,0 +1,903 @@
+/*
+ * PDKIM - a RFC4871 (DKIM) implementation
+ * Copyright (c) The Exim Maintainers 1995 - 2022
+ *
+ * signing/verification interface
+ */
+
+#include "../exim.h"
+#include "crypt_ver.h"
+#include "signing.h"
+
+
+#ifdef MACRO_PREDEF
+# include "../macro_predef.h"
+
+void
+features_crypto(void)
+{
+# ifdef SIGN_HAVE_ED25519
+ builtin_macro_create(US"_CRYPTO_SIGN_ED25519");
+# endif
+# ifdef EXIM_HAVE_SHA3
+ builtin_macro_create(US"_CRYPTO_HASH_SHA3");
+# endif
+}
+#else
+
+#ifndef DISABLE_DKIM /* rest of file */
+
+#ifdef DISABLE_TLS
+# error Must no DISABLE_TLS, for DKIM
+#endif
+
+
+/******************************************************************************/
+#ifdef SIGN_GNUTLS
+# define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3
+
+# ifndef GNUTLS_VERIFY_ALLOW_BROKEN
+# define GNUTLS_VERIFY_ALLOW_BROKEN 0
+# endif
+
+
+/* Logging function which can be registered with
+ * gnutls_global_set_log_function()
+ * gnutls_global_set_log_level() 0..9
+ */
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+static void
+exim_gnutls_logger_cb(int level, const char *message)
+{
+size_t len = strlen(message);
+if (len < 1)
+ {
+ DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
+ return;
+ }
+DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
+ message[len-1] == '\n' ? "" : "\n");
+}
+#endif
+
+
+
+void
+exim_dkim_init(void)
+{
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+DEBUG(D_tls)
+ {
+ gnutls_global_set_log_function(exim_gnutls_logger_cb);
+ /* arbitrarily chosen level; bump upto 9 for more */
+ gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
+ }
+#endif
+}
+
+
+/* accumulate data (gnutls-only). String to be appended must be nul-terminated. */
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return string_cat(g, s);
+}
+
+
+
+/* import private key from PEM string in memory.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+gnutls_datum_t k = { .data = (void *)privkey_pem, .size = Ustrlen(privkey_pem) };
+gnutls_x509_privkey_t x509_key;
+const uschar * where;
+int rc;
+
+if ( (where = US"internal init", rc = gnutls_x509_privkey_init(&x509_key))
+ || (rc = gnutls_privkey_init(&sign_ctx->key))
+ || (where = US"privkey PEM-block import",
+ rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM))
+ || (where = US"internal privkey transfer",
+ rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0))
+ )
+ return string_sprintf("%s: %s", where, gnutls_strerror(rc));
+
+switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL))
+ {
+ case GNUTLS_PK_RSA: sign_ctx->keytype = KEYTYPE_RSA; break;
+#ifdef SIGN_HAVE_ED25519
+ case GNUTLS_PK_EDDSA_ED25519: sign_ctx->keytype = KEYTYPE_ED25519; break;
+#endif
+ default: return rc < 0
+ ? CUS gnutls_strerror(rc)
+ : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc));
+ }
+
+return NULL;
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* hash & sign data. No way to do incremental.
+
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+gnutls_datum_t k_data = { .data = data->data, .size = data->len };
+gnutls_digest_algorithm_t dig;
+gnutls_datum_t k_sig;
+int rc;
+
+switch (hash)
+ {
+ case HASH_SHA1: dig = GNUTLS_DIG_SHA1; break;
+ case HASH_SHA2_256: dig = GNUTLS_DIG_SHA256; break;
+ case HASH_SHA2_512: dig = GNUTLS_DIG_SHA512; break;
+ default: return US"nonhandled hash type";
+ }
+
+if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig)))
+ return CUS gnutls_strerror(rc);
+
+/* Don't care about deinit for the key; shortlived process */
+
+sig->data = k_sig.data;
+sig->len = k_sig.size;
+return NULL;
+}
+
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+ unsigned * bits)
+{
+gnutls_datum_t k;
+int rc;
+const uschar * ret = NULL;
+
+gnutls_pubkey_init(&verify_ctx->key);
+k.data = pubkey->data;
+k.size = pubkey->len;
+
+switch(fmt)
+ {
+ case KEYFMT_DER:
+ if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER)))
+ ret = US gnutls_strerror(rc);
+ break;
+#ifdef SIGN_HAVE_ED25519
+ case KEYFMT_ED25519_BARE:
+ if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key,
+ GNUTLS_ECC_CURVE_ED25519, &k, NULL)))
+ ret = US gnutls_strerror(rc);
+ break;
+#endif
+ default:
+ ret = US"pubkey format not handled";
+ break;
+ }
+if (!ret && bits) gnutls_pubkey_get_pk_algorithm(verify_ctx->key, bits);
+return ret;
+}
+
+
+/* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental)
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
+{
+gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len };
+gnutls_datum_t s = { .data = sig->data, .size = sig->len };
+int rc;
+const uschar * ret = NULL;
+
+#ifdef SIGN_HAVE_ED25519
+if (verify_ctx->keytype == KEYTYPE_ED25519)
+ {
+ if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key,
+ GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0)
+ ret = US gnutls_strerror(rc);
+ }
+else
+#endif
+ {
+ gnutls_sign_algorithm_t algo;
+ switch (hash)
+ {
+ case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break;
+ case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break;
+ case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break;
+ default: return US"nonhandled hash type";
+ }
+
+ if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo,
+ GNUTLS_VERIFY_ALLOW_BROKEN, &k, &s)) < 0)
+ ret = US gnutls_strerror(rc);
+ }
+
+gnutls_pubkey_deinit(verify_ctx->key);
+return ret;
+}
+
+
+
+
+#elif defined(SIGN_GCRYPT)
+/******************************************************************************/
+/* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */
+
+
+/* Internal service routine:
+Read and move past an asn.1 header, checking class & tag,
+optionally returning the data-length */
+
+static int
+as_tag(blob * der, uschar req_cls, long req_tag, long * alen)
+{
+int rc;
+uschar tag_class;
+int taglen;
+long tag, len;
+
+debug_printf_indent("as_tag: %02x %02x %02x %02x\n",
+ der->data[0], der->data[1], der->data[2], der->data[3]);
+
+if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag))
+ != ASN1_SUCCESS)
+ return rc;
+
+if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND;
+
+if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0)
+ return ASN1_DER_ERROR;
+if (alen) *alen = len;
+
+/* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */
+
+der->data += taglen;
+der->len -= taglen;
+return rc;
+}
+
+/* Internal service routine:
+Read and move over an asn.1 integer, setting an MPI to the value
+*/
+
+static uschar *
+as_mpi(blob * der, gcry_mpi_t * mpi)
+{
+long alen;
+int rc;
+gcry_error_t gerr;
+
+debug_printf_indent("%s\n", __FUNCTION__);
+
+/* integer; move past the header */
+if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
+ return US asn1_strerror(rc);
+
+/* read to an MPI */
+if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL)))
+ return US gcry_strerror(gerr);
+
+/* move over the data */
+der->data += alen; der->len -= alen;
+return NULL;
+}
+
+
+
+void
+exim_dkim_init(void)
+{
+/* Version check should be the very first call because it
+makes sure that important subsystems are initialized. */
+if (!gcry_check_version (GCRYPT_VERSION))
+ {
+ fputs ("libgcrypt version mismatch\n", stderr);
+ exit (2);
+ }
+
+/* We don't want to see any warnings, e.g. because we have not yet
+parsed program options which might be used to suppress such
+warnings. */
+gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN);
+
+/* ... If required, other initialization goes here. Note that the
+process might still be running with increased privileges and that
+the secure memory has not been initialized. */
+
+/* Allocate a pool of 16k secure memory. This make the secure memory
+available and also drops privileges where needed. */
+gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0);
+
+/* It is now okay to let Libgcrypt complain when there was/is
+a problem with the secure memory. */
+gcry_control (GCRYCTL_RESUME_SECMEM_WARN);
+
+/* ... If required, other initialization goes here. */
+
+/* Tell Libgcrypt that initialization has completed. */
+gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
+
+return;
+}
+
+
+
+
+/* Accumulate data (gnutls-only).
+String to be appended must be nul-terminated. */
+
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return g; /*dummy*/
+}
+
+
+
+/* import private key from PEM string in memory.
+Only handles RSA keys.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+uschar * s1, * s2;
+blob der;
+long alen;
+int rc;
+
+/*XXX will need extension to _spot_ as well as handle a
+non-RSA key? I think...
+So... this is not a PrivateKeyInfo - which would have a field
+identifying the keytype - PrivateKeyAlgorithmIdentifier -
+but a plain RSAPrivateKey (wrapped in PEM-headers. Can we
+use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl))
+
+How does OpenSSL PEM_read_bio_PrivateKey() deal with it?
+gnutls_x509_privkey_import() ?
+*/
+
+/*
+ * RSAPrivateKey ::= SEQUENCE
+ * version Version,
+ * modulus INTEGER, -- n
+ * publicExponent INTEGER, -- e
+ * privateExponent INTEGER, -- d
+ * prime1 INTEGER, -- p
+ * prime2 INTEGER, -- q
+ * exponent1 INTEGER, -- d mod (p-1)
+ * exponent2 INTEGER, -- d mod (q-1)
+ * coefficient INTEGER, -- (inverse of q) mod p
+ * otherPrimeInfos OtherPrimeInfos OPTIONAL
+
+ * ECPrivateKey ::= SEQUENCE {
+ * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
+ * privateKey OCTET STRING,
+ * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
+ * publicKey [1] BIT STRING OPTIONAL
+ * }
+ * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it...
+
+- actually, gnutls_x509_privkey_import() appears to require a curve name parameter
+ value for that is an OID? a local-only integer (it's an enum in GnuTLS)?
+
+
+Useful cmds:
+ ssh-keygen -t ecdsa -f foo.privkey
+ ssh-keygen -t ecdsa -b384 -f foo.privkey
+ ssh-keygen -t ecdsa -b521 -f foo.privkey
+ ssh-keygen -t ed25519 -f foo.privkey
+
+ < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x
+
+ openssl asn1parse -in foo -inform PEM -dump
+ openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??)
+(not good for ed25519)
+
+ */
+
+if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----"))
+ || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" ))
+ )
+ return US"Bad PEM wrapper";
+
+*s2 = '\0';
+
+if ((rc = b64decode(s1, &der.data) < 0))
+ return US"Bad PEM-DER b64 decode";
+der.len = rc;
+
+/* untangle asn.1 */
+
+/* sequence; just move past the header */
+if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+ != ASN1_SUCCESS) goto asn_err;
+
+/* integer version; move past the header, check is zero */
+if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
+ goto asn_err;
+if (alen != 1 || *der.data != 0)
+ return US"Bad version number";
+der.data++; der.len--;
+
+if ( (s1 = as_mpi(&der, &sign_ctx->n))
+ || (s1 = as_mpi(&der, &sign_ctx->e))
+ || (s1 = as_mpi(&der, &sign_ctx->d))
+ || (s1 = as_mpi(&der, &sign_ctx->p))
+ || (s1 = as_mpi(&der, &sign_ctx->q))
+ || (s1 = as_mpi(&der, &sign_ctx->dp))
+ || (s1 = as_mpi(&der, &sign_ctx->dq))
+ || (s1 = as_mpi(&der, &sign_ctx->qp))
+ )
+ return s1;
+
+#ifdef extreme_debug
+DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n");
+ {
+ uschar * s;
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n);
+ debug_printf_indent(" N : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e);
+ debug_printf_indent(" E : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d);
+ debug_printf_indent(" D : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p);
+ debug_printf_indent(" P : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q);
+ debug_printf_indent(" Q : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp);
+ debug_printf_indent(" DP: %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq);
+ debug_printf_indent(" DQ: %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp);
+ debug_printf_indent(" QP: %s\n", s);
+ }
+#endif
+
+sign_ctx->keytype = KEYTYPE_RSA;
+return NULL;
+
+asn_err: return US asn1_strerror(rc);
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* sign already-hashed data.
+
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+char * sexp_hash;
+gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL;
+gcry_mpi_t m_sig;
+uschar * errstr;
+gcry_error_t gerr;
+
+/*XXX will need extension for hash types (though, possibly, should
+be re-specced to not rehash but take an already-hashed value? Actually
+current impl looks WRONG - it _is_ given a hash so should not be
+re-hashing. Has this been tested?
+
+Will need extension for non-RSA sugning algos. */
+
+switch (hash)
+ {
+ case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
+ case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
+ default: return US"nonhandled hash type";
+ }
+
+#define SIGSPACE 128
+sig->data = store_get(SIGSPACE, GET_UNTAINTED);
+
+if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0)
+ {
+ gcry_mpi_swap (sign_ctx->p, sign_ctx->q);
+ gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q);
+ }
+
+if ( (gerr = gcry_sexp_build (&s_key, NULL,
+ "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))",
+ sign_ctx->n, sign_ctx->e,
+ sign_ctx->d, sign_ctx->p,
+ sign_ctx->q, sign_ctx->qp))
+ || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
+ (int) data->len, CS data->data))
+ || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key))
+ )
+ return US gcry_strerror(gerr);
+
+/* gcry_sexp_dump(s_sig); */
+
+if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0))
+ )
+ return US"no sig result";
+
+m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG);
+
+#ifdef extreme_debug
+DEBUG(D_acl)
+ {
+ uschar * s;
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig);
+ debug_printf_indent(" SG: %s\n", s);
+ }
+#endif
+
+gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig);
+if (gerr)
+ {
+ debug_printf_indent("signature conversion from MPI to buffer failed\n");
+ return US gcry_strerror(gerr);
+ }
+#undef SIGSPACE
+
+return NULL;
+}
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+ unsigned * bits)
+{
+/*
+in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
+*/
+uschar tag_class;
+int taglen;
+long alen;
+unsigned nbits;
+int rc;
+uschar * errstr;
+gcry_error_t gerr;
+uschar * stage = US"S1";
+
+if (fmt != KEYFMT_DER) return US"pubkey format not handled";
+
+/*
+sequence
+ sequence
+ OBJECT:rsaEncryption
+ NULL
+ BIT STRING:RSAPublicKey
+ sequence
+ INTEGER:Public modulus
+ INTEGER:Public exponent
+
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head;
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump;
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22;
+*/
+
+/* sequence; just move past the header */
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+ != ASN1_SUCCESS) goto asn_err;
+
+/* sequence; skip the entire thing */
+DEBUG(D_acl) stage = US"S2";
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen))
+ != ASN1_SUCCESS) goto asn_err;
+pubkey->data += alen; pubkey->len -= alen;
+
+
+/* bitstring: limit range to size of bitstring;
+move over header + content wrapper */
+DEBUG(D_acl) stage = US"BS";
+if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS)
+ goto asn_err;
+pubkey->len = alen;
+pubkey->data++; pubkey->len--;
+
+/* sequence; just move past the header */
+DEBUG(D_acl) stage = US"S3";
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+ != ASN1_SUCCESS) goto asn_err;
+
+/* read two integers */
+DEBUG(D_acl) stage = US"MPI";
+nbits = pubkey->len;
+if ((errstr = as_mpi(pubkey, &verify_ctx->n))) return errstr;
+nbits = (nbits - pubkey->len) * 8;
+if ((errstr = as_mpi(pubkey, &verify_ctx->e))) return errstr;
+
+#ifdef extreme_debug
+DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n");
+ {
+ uschar * s;
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n);
+ debug_printf_indent(" N : %s\n", s);
+ gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e);
+ debug_printf_indent(" E : %s\n", s);
+ }
+
+#endif
+if (bits) *bits = nbits;
+return NULL;
+
+asn_err:
+DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc));
+ return US asn1_strerror(rc);
+}
+
+
+/* verify signature (of hash)
+XXX though we appear to be doing a hash, too!
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
+{
+/*
+cf. libgnutls 2.8.5 _wrap_gcry_pk_verify()
+*/
+char * sexp_hash;
+gcry_mpi_t m_sig;
+gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL;
+gcry_error_t gerr;
+uschar * stage;
+
+/*XXX needs extension for SHA512 */
+switch (hash)
+ {
+ case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
+ case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
+ default: return US"nonhandled hash type";
+ }
+
+if ( (stage = US"pkey sexp build",
+ gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))",
+ verify_ctx->n, verify_ctx->e))
+ || (stage = US"data sexp build",
+ gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
+ (int) data_hash->len, CS data_hash->data))
+ || (stage = US"sig mpi scan",
+ gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL))
+ || (stage = US"sig sexp build",
+ gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig))
+ || (stage = US"verify",
+ gerr = gcry_pk_verify (s_sig, s_hash, s_pkey))
+ )
+ {
+ DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage);
+ return US gcry_strerror(gerr);
+ }
+
+if (s_sig) gcry_sexp_release (s_sig);
+if (s_hash) gcry_sexp_release (s_hash);
+if (s_pkey) gcry_sexp_release (s_pkey);
+gcry_mpi_release (m_sig);
+gcry_mpi_release (verify_ctx->n);
+gcry_mpi_release (verify_ctx->e);
+
+return NULL;
+}
+
+
+
+
+#elif defined(SIGN_OPENSSL)
+/******************************************************************************/
+
+void
+exim_dkim_init(void)
+{
+ERR_load_crypto_strings();
+}
+
+
+/* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too
+because now using hash-and-sign interface) */
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return string_cat(g, s);
+}
+
+
+/* import private key from PEM string in memory.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+BIO * bp = BIO_new_mem_buf((void *)privkey_pem, -1);
+
+if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL)))
+ return string_sprintf("privkey PEM-block import: %s",
+ ERR_error_string(ERR_get_error(), NULL));
+
+sign_ctx->keytype =
+#ifdef SIGN_HAVE_ED25519
+ EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519
+ ? KEYTYPE_ED25519 : KEYTYPE_RSA;
+#else
+ KEYTYPE_RSA;
+#endif
+return NULL;
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* hash & sign data. Incremental not supported.
+
+Return: NULL for success with the signaature in the sig blob, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+const EVP_MD * md;
+EVP_MD_CTX * ctx;
+size_t siglen;
+
+switch (hash)
+ {
+ case HASH_NULL: md = NULL; break; /* Ed25519 signing */
+ case HASH_SHA1: md = EVP_sha1(); break;
+ case HASH_SHA2_256: md = EVP_sha256(); break;
+ case HASH_SHA2_512: md = EVP_sha512(); break;
+ default: return US"nonhandled hash type";
+ }
+
+#ifdef SIGN_HAVE_ED25519
+if ( (ctx = EVP_MD_CTX_new())
+ && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
+ && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0
+ && (sig->data = store_get(siglen, GET_UNTAINTED))
+
+ /* Obtain the signature (slen could change here!) */
+ && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0
+ )
+ {
+ EVP_MD_CTX_destroy(ctx);
+ sig->len = siglen;
+ return NULL;
+ }
+#else
+/*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */
+if ( (ctx = EVP_MD_CTX_create())
+ && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
+ && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0
+ && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0
+ && (sig->data = store_get(siglen, GET_UNTAINTED))
+
+ /* Obtain the signature (slen could change here!) */
+ && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0
+ )
+ {
+ EVP_MD_CTX_destroy(ctx);
+ sig->len = siglen;
+ return NULL;
+ }
+#endif
+
+if (ctx) EVP_MD_CTX_destroy(ctx);
+return US ERR_error_string(ERR_get_error(), NULL);
+}
+
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+ unsigned * bits)
+{
+const uschar * s = pubkey->data;
+uschar * ret = NULL;
+
+switch(fmt)
+ {
+ case KEYFMT_DER:
+ /*XXX hmm, we never free this */
+ if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len)))
+ ret = US ERR_error_string(ERR_get_error(), NULL);
+ break;
+#ifdef SIGN_HAVE_ED25519
+ case KEYFMT_ED25519_BARE:
+ if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL,
+ s, pubkey->len)))
+ ret = US ERR_error_string(ERR_get_error(), NULL);
+ break;
+#endif
+ default:
+ ret = US"pubkey format not handled";
+ break;
+ }
+
+if (!ret && bits) *bits = EVP_PKEY_bits(verify_ctx->key);
+return ret;
+}
+
+
+
+
+/* verify signature (of hash, except Ed25519 where of-data)
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig)
+{
+const EVP_MD * md;
+
+switch (hash)
+ {
+ case HASH_NULL: md = NULL; break;
+ case HASH_SHA1: md = EVP_sha1(); break;
+ case HASH_SHA2_256: md = EVP_sha256(); break;
+ case HASH_SHA2_512: md = EVP_sha512(); break;
+ default: return US"nonhandled hash type";
+ }
+
+#ifdef SIGN_HAVE_ED25519
+if (!md)
+ {
+ EVP_MD_CTX * ctx;
+
+ if ((ctx = EVP_MD_CTX_new()))
+ {
+ if ( EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0
+ && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0
+ )
+ { EVP_MD_CTX_free(ctx); return NULL; }
+ EVP_MD_CTX_free(ctx);
+ }
+ }
+else
+#endif
+ {
+ EVP_PKEY_CTX * ctx;
+
+ if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)))
+ {
+ if ( EVP_PKEY_verify_init(ctx) > 0
+ && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0
+ && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0
+ && EVP_PKEY_verify(ctx, sig->data, sig->len,
+ data->data, data->len) == 1
+ )
+ { EVP_PKEY_CTX_free(ctx); return NULL; }
+ EVP_PKEY_CTX_free(ctx);
+
+ DEBUG(D_tls)
+ if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0)
+ debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n",
+ (int) sig->len, EVP_PKEY_size(verify_ctx->key));
+ }
+ }
+
+return US ERR_error_string(ERR_get_error(), NULL);
+}
+
+
+
+#endif
+/******************************************************************************/
+
+#endif /*DISABLE_DKIM*/
+#endif /*MACRO_PREDEF*/
+/* End of File */
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-03 12:27:02 +0000